At least one person was killed at the rally, with as many as eight shots fired. The gunman was killed immediately after the shots were fired. Two more are critically injured.
Mr Trump was rushed to a nearby hospital but was quickly discharged.
Witnesses at the rally say they warned the police about a gunman on the roof moments before several shots rung out.
A witness told Newsnight: “We’re pointing at the guy crawling up the roof…he had a rifle. We could clearly see him with a rifle, absolutely.
“We’re pointing at him, the police are down there running around on the ground, we’re like ‘hey man, there’s a guy on the roof with a rifle’, and the police are like ‘huh’.”
He continued: “Next thing you know, I’m thinking to myself, ‘why is Trump still speaking, why have they not pulled him off the stage?’”
